// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_TEXT_RANGES_H_
#define MEDIA_BASE_TEXT_RANGES_H_

#include <stddef.h>

#include <map>

#include "base/macros.h"
#include "base/time/time.h"
#include "media/base/media_export.h"

namespace media {

// Helper class used by the TextRenderer to filter out text cues that
// have already been passed downstream.
class MEDIA_EXPORT TextRanges {
public:
    TextRanges();
    ~TextRanges();

    // Reset the current range pointer, such that we bind to a new range
    // (either one that exists already, or one that is freshly-created)
    // during the next AddCue().
    void Reset();

    // Given a cue with starting timestamp |start_time|, add its start
    // time to the time ranges. (Note that following a Reset(), cue
    // times are assumed to be monotonically increasing.) If this time
    // has already been added to the time ranges, then AddCue() returns
    // false and clients should not push the cue downstream. Otherwise,
    // the time is added to the time ranges and AddCue() returns true,
    // meaning that the cue should be pushed downstream.
    bool AddCue(base::TimeDelta start_time);

    // Returns a count of the number of time ranges, intended for use by
    // the unit test module to vet proper time range merge behavior.
    size_t RangeCountForTesting() const;

private:
    // Describes a range of times for cues that have already been
    // pushed downstream.
    class Range {
    public:
        // Initialize last_time count.
        void ResetCount(base::TimeDelta start_time);

        // Set last_time and associated counts.
        void SetLastTime(base::TimeDelta last_time);

        // Adjust time range state to mark the cue as having been seen,
        // returning true if we have not seen |start_time| already and
        // false otherwise.
        bool AddCue(base::TimeDelta start_time);

        // Returns the value of the last time in the range.
        base::TimeDelta last_time() const;

    private:
        // The last timestamp of this range.
        base::TimeDelta last_time_;

        // The number of cues we have detected so far, for this range,
        // whose timestamp matches last_time.
        int max_count_;

        // The number of cues we have seen since the most recent Reset(),
        // whose timestamp matches last_time.
        int count_;
    };

    typedef std::map<base::TimeDelta, Range> RangeMap;

    // NewRange() is used to create a new time range when AddCue() is
    // called immediately following a Reset(), and no existing time
    // range contains the indicated |start_time| of the cue.
    void NewRange(base::TimeDelta start_time);

    // Coalesce curr_range with the range that immediately follows.
    void Merge(Range& curr_range, const RangeMap::iterator& next_range_itr);

    // The collection of time ranges, each of which is bounded
    // (inclusive) by the key and Range::last_time.
    RangeMap range_map_;

    // The time range to which we bind following a Reset().
    RangeMap::iterator curr_range_itr_;

    DISALLOW_COPY_AND_ASSIGN(TextRanges);
};

} // namespace media

#endif // MEDIA_BASE_TEXT_RANGES_H_
